PATIENT CHARACTERISTICS: Age: Over 18 Performance status: Zubrod 0-1 Life expectancy: More than 12 weeks Hematopoietic: Hemoglobin greater than lower limit of normal WBC greater than 3,000/mm3 Platelet count greater than 125,000/mm3 No significant bleeding disorder Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) AST/ALT no greater than 1.5 times ULN No chronic or acute hepatic disorder Renal: BUN no greater than 1.5 times ULN Creatinine no greater than 1.5 times ULN No chronic or acute renal disorder Gastrointestinal: No diagnosis or treatment of esophageal, gastric, pyloric channel, or duodenal ulceration within past 30 days No prior or active pancreatic disease or inflammatory bowel disease (e.g., Crohn's disease or ulcerative colitis) Other: Completed a smoking cessation program, if applicable No prior hypersensitivity to COX-2 inhibitors, NSAIDs, salicylates, or sulfonamides No prior invasive cancer within the past 5 years except non-melanoma skin cancer or carcinoma in situ of the cervix No other concurrent condition that would preclude study Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception